Well, I've been wondenring how do Passive RFIDs work...
"Well, it's easy..." you can say.
I know the basics: the tag uses the magnetic field from the reader to power up the LC Circuit. The capacitor is then charged and then discharged and charged and then discharged (with opposite flow direction) ad infinitum
(or until there's no energy)... and this is the phenomena that generates the Radio Wave.
Now, my question is, how does the chip encode the data in the wave?
I thought of PWM, but that would imply the circuit to be turned-on and off and I can't think on that...
So how is the modulation of the wave done by the chip?
To modulate the wave in amplitude, the chip could have a variable resistor that would be very high on a 0 and low on a 1, right? Still, I guess RFID do not use AM. :-?
P.S.: This is not related directly to Arduino, but there are people here who have knowledge on electronics, so